1. Field of the Invention
The present invention relates to an applicator for use in hyperthermia, and, more particularly, to an applicator for use in hyperthermia which is used to treat a predetermined location within a human body by locally applying heat thereto by means of electromagnetic waves.
2. Prior Art
Lately, hyperthermia has been attracting attention. Recent researches (including that reported on Page 14 of MICROWAVES, October, 1976) have shown that, if heat is continuously applied to a malignant tumor at a temperature of about 43.degree. C. for an hour or two, and this application of heat is repeated at regular intervals, it is possible to impede the regeneration of cancer cells and simultaneously kill most of them. Hyperthermia of this type falls into two categories: general hyperthermia and local hyperthermia. In local hyperthermia, in which cancerous tissue and its surroundings are selectively heated, methods using electromagnetic waves, electromagnetic induction, or ultrasonic waves have been proposed.
The present inventors have proposed and are containing to research the treatment of cancers located deep in the human body by means of electromagnetic waves. In such treatment, it is necessary to focus the electromagnetic energy when transmitting the electromagnetic waaves into the body. For this purpose, the present inventors have incorporated an electromagnetic lens in a heating applicator. An applicator 1 adopted by the present inventors, as shown in FIG. 1, is composed of a casing 3 which functions as a waveguide, a wave supply portion 2 provided at one end of the casing 3, and an electromagnetic lens portion 4 provided at the other end of the casing 3. The output side of the electromagnetic lens portion 4 is provided with a solid cooling plate 5 which prevents the surface of the body from overheating, and which employs cooling water.
However, this conventional applicator suffers from the following disadvantages:
(1) In the applicator, electromagnetic waves are reflected by the electromagnetic lens or coolant, generating a large amount of energy loss of electromagnetic waves. This causes the output of the applicator to be lowered.
(2) Loss of electromagnetic wave energy occurring in the applicator causes the applicator to overheat, making the handling of the applicator difficult.
(3) The raised temperature of the applicator invites thermal expansion of the fluid such as machine oil which is accommodated in the applicator. This can lead to damage of the applicator.